In a Long Term Evolution (LTE) system, a demodulation reference signal (DMRS) is a downlink reference signal sent by a base station to user equipment (UE). The UE may perform channel estimation on a physical resource block (PRB) based on the DMRS, and demodulate data on the physical resource block based on a channel estimation result.
DMRSs need to be transmitted in a relatively-high-density manner to obtain a relatively good channel estimation effect. In an LTE specification, the DMRSs have two alternative time-frequency distribution patterns in one physical resource block. One PRB includes two slots. Each slot includes seven or six symbols in a time domain dimension and 12 subcarriers in a frequency domain dimension. A first pattern of the DMRSs is: The DMRSs occupy last two symbols of each slot in the time domain dimension, and occupy subcarriers 1, 6, and 11 in the frequency domain dimension. A second pattern of the DMRSs is: The DMRSs are divided into two groups, each occupying last two symbols of each slot in the time domain dimension. A first group of DMRSs occupies subcarriers 1, 6, and 11 in the frequency domain dimension, and a second group of DMRSs occupies subcarriers 0, 5, and 10 in the frequency domain dimension.
If a better channel estimation effect needs to be obtained, the DMRSs usually need to be sent on more time-frequency resources. However, this leads to additional radio resource overheads and reduces a throughput of a communications system.